Silk screen printing machine having variable printing length

ABSTRACT

In a silk screen machine having a rotatable drum, the turning of the drum is controlled in such a manner that the drum starts each printing movement or the arc of its angular movement from a fixed starting position. The rotation of the drum is set to an angular value which in general corresponds substantially to the length of the material to be printed.

United States Patent Svantesson et a1. Oct. 28, 1975 [54] SILK SCREEN PRINTING MACHINE 2,581,775 l/1952 Wade 101/123 HAVING VARIABLE PRINTING LENGTH 2,606,492 8/1952 Black 101/124 2,702,001 2/1955 Gattuso [01/124 1 Inventors: Ake n s Trenvagen 28, 141 2,866,404 12/1958 Laupman 101/123 Huddfngei FOREIGN PATENTS OR APPLICATIONS LInneaStIgen 13, 150 24 Ronmnge, both f Sweden 2,005,101 8/1971 Germany 101/116 1,038,067 9/1958 Germany 101/114 [22] Filed: June 27, 1972 1,207,836 2/1960 France 101/123 1,047,214 12/1958 Germany 101/124 [21] APPL 266,598 665,816 7/1963 Canada 101/124 Foreign Application Priority Data Primary Examiner-Clifford Crowder Assistant Examiner-R. E. Suter J 1 8, 1971 S d u y en 8833/7 Alwrney, Agent, or FIrmEr1c Y. Munson [52] U.S. Cl 101/124; 101/126 51 Int. c1. B41F 15/10; B41F 15/22 [57] ABSTRACT [58] Fi ld f S h 101 211, 12 124 114 In a silk screen machine having a rotatable drum, the 101/115, 116, 277, 278, 282, 250, 251, 252 turning of the drum is controlled in such a manner that the drum starts each printing movement or the 5 References Cited arc of its angular movement from a fixed starting posi- UNITED STATES PATENTS tion. The rotation of the drum is set to an angular l 549 533 8,1925 F l 0l/ value which in general corresponds substantially to the rIe 1,832,216 11/1931 Johnson et al length of the mammal to be pnnted' 2,105,328 1/1938 Molitor 101/282 2 Claims, 1 Drawing Figure US. Patent Oct. 28, 1975 SILKSCREEN PRINTING MACHINE HAVING VARIABLE PRINTING LENGTH BACKGROUND OF THE INVENTION The present invention relates to stencil or silk screen printing machines and more specifically to the type of printing machines using a reciprocatingly rotatable drum having means for holding the material to be printed. With such printing machines, a frame for receiving and holding the stencil or screen is arranged for tangential movement on and around the periphery of the drum in response to rotary or angular movement of the drum, in a manner to prevent translational displacement of the frame relative to the peripheral surface of the drum. Further, a squeegee is placed to engage the stencil adjacent the drum at the region where the stencil or screen tangentially engages the drum, the squeegee being arranged for movement to and away from the screen and the drum. The squeegee structure is supported on the frame or main body of the machine by suitable means. Further, the squeegee means is positioned on the side of the stencil away from the drum and is employed to transfer colour paste to the stencil to be delivered to the material to be printed.

Stencil or silk screen printing machines of the aforementioned type are known to the art and are con structed for relatively high printing speed. It has been discovered in practice, however, that there is a limit to the speed at which such machines can perform printing work. This is primarily due to the fact that the printing speed is dependent on the speed at which the drum operates during a printing sequence, and thus the drum operating speed must be well adjusted in order to obtain a good printing result. Since the mechanism used to drive the drum during a printing sequence is also utilized to return the drum to the starting position, the total printing time is the sum of the two periods of time one period taken to effect a printing sequence, and the other period to return the drum to its starting position, the time taken for each being the same.

OBJECTS OF THE PRESENT INVENTION.

The object of the present invention is to provide an adjustable mechanism for controlling and regulating the angular movement of the drum. Thus, in accordance with the present invention means are provided whereby angular movement of the drum can be adjusted to a pre-determined magnitude, which preferably only slightly exceeds, but which, in general, substantially corresponds to the length of the material to be printed. Such regulating possibilities are not found in known stencil printing machines.

DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT.

It is not considered necessary to show all facts of the printing machine for a clear understanding of the invention, only those necessary co-operating facts are shown that relate to the improvement here involved. The invention is directed to the combination in which means are provided for adjusting the angular movement of the conventional drum to relate the length of a peripheral movement of the drum to the length of the material to be imprinted. Therefore, only that adjusting mechanism is shown and explained, in relation to the drum and screen frame.

Theinvention will now be described in more detail with reference to an embodiment thereof illustrated in the accompanying drawing, further features of the invention being made apparent in connection therewith. The single figure of the drawing illustrates diagrammatically an embodiment of the invention with which an adjustment of the angular movement of the drum can be made.

The drawing illustrates in simplified form and diagrammatically a stencil printing machine or silk screen machine employing a reciprocatingly rotatable drum or shell 1. Located on the drum is a suitable means 2 for holding the edge portion of the material 3 to be printed. A frame 4 is provided to hold a stencil 5 and is preferably arranged for linear movement along the periphery of the drum 1 in response to rotation of the drum. This coordination of movement is known per se, and is not indicated in the accompanying drawing. Briefly, however, such arrangements normally comprise a rack (not shown) which extends along the: frame and co-acts with a pinion wheel (not shown) arranged on the drum 1. A squeegee means 6 is disposed to engage the screen wipingly behind the tangential region of engagement of the screen with the drum, during the printing or forward movement and operation of the screen, and the squeegee is controlled to be retracted from the screen during the return movement of the screen to its initial starting position. The squeegee is illustrated in the drawing occupying the printing positions. Located immediately adjacent the squeegee 6 is a colour paste filling means 7, which is also mounted for movement to and away from the screen.

The drum 1 is mounted for rotation around a centre shaft 10, onto which is mounted a gear 11. The gear 11 meshes with a toothed arc 12 connected with and carried by a segment 13 which is mounted for pivotal angular oscillation on a shaft 14. The segment 13 carries a bearing pin means 16 located between the toothed are 12 and the shaft 14. The bearing pin 16 pivotally supports one end of a connecting rod 15, and the other end, 1512. of the rod 15. is pivoted on a second bearing pin 17 supported on a bracket 18 adjustably positionable on an arcuate lever arm 19 to vary the angular throw of the segment 13 to control the angular movement of the drum. The arcuate lever arm 19 preferably of rectangular cross section, has one end 19b mounted for pivotal movement around a pin 20. The bracket 18 is constructed so that it can be securely fixed to the bar 19 at any position therealong, to which it is adjusted.

The end 19b of the lever arm 19 is securely mounted to one end 21a of a crank arm 21, also mounted for pivotal movement about said pin 20. The other end 21b of crank arm 21 is provided with a bearing pin 22 that pivotally supports one end 23a of a connecting crank rod 23, the other end 23b of which is pivotally supported on a crank pin 24, at the end of a crank 25. The crank 25 is secured to a rotatable shaft carrying a toothed wheel 26 driven by a transmission means 27 from an electric motor 28, the output shaft 28 of which drives a gear 29 for the belt 27.

The crank 25 of the illustrated embodiment is assumed to be driven at a constant speed.

Although the transmission means 27 in the illustrated embodiment is shown in the form of a chain drive (the chain being shown in morse lines. in the drawing), it will readily be perceived that the transmission chain 27 can be in the form of a belt drive or similar drive, while at the same time the crank 25 may be driven at different speeds, for example by means of a speed change gear.

The means 18 is securely mounted to the bar in any selected setting position by means of known arrangements.

The mechanism operates in the following manner: Since the crank 25 is arranged to rotate at a selected speed, the arm will impart to the toothed are 12 an angular movement via the connecting rods 23 and 21 and the lever 19. The magnitude of the angular movement of the segment 13 is dependent on the location of the bracket 18 on the lever 19. Thus the effective length of lever 19, as a radius lever around pin 20, determines the throw at pin 16 and the angular movement of segment 13. Further, the lever is arcuate in shape with the radius of the arc corresponding substantially to the length of the connecting rod 15. The axis of pin 16 is the centre of the are represented by the bar 19, when the device is in the shown position that is the starting position. This arrangement ensures that the holding means 2, for holding the edge portion of the material 3 to be, always constantly takes a predetermined position in relation to the squeegee 6 and the stencil 5, irrespective of the position in at which the bracket 18 is set along the arcuate lever 19.

When the crank 25 is rotated clockwise at the selected angular speed, it will readily be seen that the connecting rod 15 will be moved to the left in the drawing, causing angular movement of the toothed arc 12 around its shaft 14, and thereby also causing rotation of the drum 1 in the printing sequence. After movement of the connecting rod 15 to the extent permitted by the arrangement of crank arm 21 arcuate lever 19, the connecting bar 15 begins to return to its starting position, whereupon the drum 1, in turn, is moved back to its starting position. In this starting position of drum 1, a new sheet 3 of material to be printed is placed in the sheet retaining means 2 and a new printing sequence is begun. Owing to the fact that it is possible to regulate the angular movement of the drum 1, the advantage is obtained whereby total angular movement of the drum can be set at a value which preferably only slightly exceeds, but which in general substantially corresponds to, the length of the material to be printed. Thus, when the sheet of material to be printed is of short length, the drum movement can be adjusted to a smaller total angle.

Although the invention has been described with reference to a preferred embodiment thereof, it will be understood that the invention is not restricted thereto but can be modified within the scope of the inventive concept. Thus, although the preferred embodiment shows an arrangement 18 co-acting with a lever 19, it will be obvious that alternative constructions can be applied.

1. A stencil printing machine comprising:

a. a reciprocating frame supporting a stencil;

b. a drum mounted on a central shaft to oscillate the former in opposite directions;

c. said drum being mechanically coupled to said frame to impart translatory movement thereto in opposite directions corresponding to the direction of the oscillatory movement of the drum;

(1. a drive motor;

e. coupling means for mechanically linking said motor to said drum to turn the latter first in one direction for a printing operation and then in reverse direction to a predetermined starting position so as to cause each printing operation to commence from the same starting position;

f. means for adjusting said coupling means to control the oscillatory motion of the drum for different lengths of material to be printed:

g. said adjusting means comprising i. a gear ring mounted co-axially with said drum; ii. a pivoted sector member having a toothed are engaging said gear ring;

iii. an arcuate lever having one end pivoted on a shaft, the other end being free;

iv. a connecting rod having one end connected to said arcuate lever, the other end being connected to said sector member for oscillating said drum;

v. crank means driven by said motor and connected to said lever shaft to turn the pivoted end of the lever in a hypothetical sector are of a predetermined angle;

vi. said connecting rod being adjustable on said arcuate lever to a position which corresponds to the axis of said sector arc;

vii. the length of the arm of said connecting rod in said adjusted position being equal to the length of the radius of said sector arc.

2. A stencil printing machine according to claim 1 in which a squeegee is mounted above the drum to engage the stencil in the region where the stencil tangentially engages the drum and which squeegee is mounted for movement to and away from the stencil and the drum.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Pa 3,915,088 Dated October 28, 1975 lnventofls) Ake Svantesson, Astor Lindstrom It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Claim 1, Line 40, delete "axis of said sector are and insertlength of the printing operation-- Lines 41-42, delete "in said adjusted Signed and Scaled this Thirty-first Da of August 1976 position".

. A ttest:

RUTH C. MASON Commissioner ofParems and Trademarks 

1. A stencil printing machine comprising: a. a reciprocating frame supporting a stencil; b. a drum mounted on a central shaft to oscillate the former in opposite directions; c. said drum being mechanically coupled to said frame to impart translatory movement thereto in opposite directions corresponding to the direction of the oscillatory movement of the drum; d. a drive motor; e. coupling means for mechanically linking said motor to said drum to turn the latter first in one direction for a printing operation and then in reverse direction to a predetermined starting position so as to cause each printing operation to commence from the same starting position; f. means for adjusting said coupling means to control the oscillatory motion of the drum for different lengths of material to be printed: g. said adjusting means comprising i. a gear ring mounted co-axially with said drum; ii. a pivoted sector member having a toothed arc engaging said gear ring; iii. an arcuate lever having one end pivoted on a shaft, the other end being free; iv. a connecting rod having one end connected to said arcuate lever, the other end being connected to said sector member for oscillating said drum; v. crank means driven by said motor and connected to said Lever shaft to turn the pivoted end of the lever in a hypothetical sector arc of a predetermined angle; vi. said connecting rod being adjustable on said arcuate lever to a position which corresponds to the axis of said sector arc; vii. the length of the arm of said connecting rod in said adjusted position being equal to the length of the radius of said sector arc.
 2. A stencil printing machine according to claim 1 in which a squeegee is mounted above the drum to engage the stencil in the region where the stencil tangentially engages the drum and which squeegee is mounted for movement to and away from the stencil and the drum. 